Syngas Fuel Hybrid 45 MW GTCC/ORC Power Plant Using Modular 500 TPD Coal/Biomass Modular Pyrolytic Gasification

This paper presents a solution for developing economies where power shortages require power plants in the range of 30/50 MW or larger to support industrial facilities such as mining or industrial parks where natural gas is not available and where diesel fuel is expensive, but where coal is readily available. Recent developments with Pyrolytic gasification systems by Wiley Consulting, capable of modular 500tpd of coal or biomass, were investigated for power starved sub-Saharan African countries. This Gasifier does not require an oxygen plant and produces a Syngas that can be combusted in modified FR6B gas turbines. The Syngas needs to be compressed and the parasitic load is accommodated with steam injection for NOx control and power enhancement to power the fuel gas compressor. To simplify the exhaust heat power recovery, the Cascading Closed Loop Cycle (CCLC) Organic Rankine Cycle (ORC) system was integrated into this system, resulting in a nominal 45 MW coal or biomass power plant at altitudes over 1000m achieving 40%+ efficiency. Coal fired steam plant Rankine cycle was considered expensive and inefficient due to the requirements of low emissions as well as more than 70% of the fuel energy rejected in the condensing system. Using the Gas Turbine Brayton cycle to combust Synthesis Gas (produced by an innovative Pyrolytic and modular gasification process that did not need an oxygen plant) was considered a practical alternative, especially as the Gas Turbine is air cooled. To fully capture the value of the Syngas fuel, the Gas Turbine exhaust energy would be recovered in an ORC which avoided the use of water and provided excellent load following characteristics as well as the capability to turndown to 40% or lower loads. The criteria established for the power plant was to build and commission the plant in 24 months or less. This necessitated looking at available used and refurbished generating equipment. The modular Gasifier, already demonstrated as a 250 tpd system, could readily be scaled to 500 tpd coal or biomass with about the same footprint and dispatched in modules for fast installation. The availability of a used 38 MW class GT for refurbishment and modification to Syngas fuel combustion system allowed site installation within one year and the provision of emergency power using available diesel fuel. This paper will fully describe the 45 MWe Hybrid GT/ORC Combined Cycle power plant utilizing the innovative Pyrolytic coal gasification process as the fuel source for an efficient low emissions power supply.